Two-temperature refrigerating system



NOV. 23, 1948. w, c so 2,454,537

TWO TEMPERATURE REFRIGERATING SYSTEM Filed May 5, 1947 Fi gl.

Inventor"; Leonard W. Acchrson,

T'hs Attovney.

Patented Nov. 23, 1948 TWO-TEMPERATURE BEFBIGEBATING SYSTEM Leonard W.Atchison, Erie, Pa., auignor to General Electric Company,

York

a corporation of New Application May 5, 1947, Serial No. 745,840

4 Claims.

My invention relates to refrigerating systems and particularly tosystems employing a plurality of evaporators for operation at differenttemperatures.

Some refrigerators, particularly those intended to accommodatesubstantial quantities of frozen foods, include separate compartmentsoperating at different temperatures. Where separate evaporatorr. areprovided for refrigerating these compartments it is desirable that theflow of refrigerant through the evaporators be controlled in a mannerwhich will enable maintenance of the proper temperature in eachevaporator.

It is an object of my invention to provide a two-temperaturerefrigerating system employing two evaporators and including an improvedarrangement for controlling the flow of refrigerant through theevaporators.

It is another object of my invention to control the flow of vaporizedrefrigerant from the evaporators in such a manner that one evaporator ata time will be automatically connected to the suction line of thesystem.

It is a further object of my invention to provide a two-temperaturerefrigerating system employing two evaporators wherein the connection ofone evaporator to the suction line is dependent on the closing of thepassage from the other evaporator to the suction line.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a betterunderstanding of my invention reference may be had to theaccompanying drawing in which Fig. 1 illustrates schematically atwo-temperature refrigerating system incorporating an embodiment of myinvention; and Fig. 2 shows details of a check valve forming part of thesystem.

Referring now to Fig. 1 I have there shown a two-temperaturerefrigerating system which includes a compressor i, a condenser 2, a lowtemperature evaporator 3, and a higher temperature evaporator 4. Thecompressor may be driven by an electric motor 5, which is connected tothe compressor in any suitable manner.

Liquid refrigerant is supplied to the system from the condenser througha restricting tube 6.

vaporized refrigerant is withdrawn from the system by the compressorthrough a suction line I which is connected by means of two branchconduits 8 and 9 to the low temperature evaporator I and the highertemperature evaporator 4 respectively. In order to provide additionalcooling for the liquid refrigerant in the restricting tube i and tovaporize any liquid refrigerant withdrawn through the suction line I,the liquid line and the suction line are placed in heat exchangerelation through a portion of their lengths, as indicated at II in thedrawing.

The liquid refrigerant supplied through the restricting tube I isconducted to the higher temperature evaporator 4. This evaporator isprovided with a header II from which vaporized refrigerant may bewithdrawn and from which liquid refrigerant is supplied to the lowtemperature evaporator 3. Liquid refrigerant is supplied to the lowtemperature evaporator 3 through a second restricting tube l2 which isconnected to the header II at the normal liquid level of the refrigeranttherein. The low temperature evaporator I is provided with a header itfrom which the vaporized refrigerant is withdrawn through the conduit i.

My arrangement for controlling the operation of the refrigerating systemto provide for the operation of the evaporators at differenttemperatures includes the provision of suitable pressureinfluenceddevices in the branch suction conduits l and 9 which provide passagesfor vaporized refrigerant from the evaporators to the suction line I.

In order to control the flow of vaporized refrigerant from the highertemperature evaporator 4, a flow-controlling device or valve M, which isresponsive to the pressure in the higher temperature evaporator, isprovided. .The valve il includes a housing composed of two parts l5 andi8 between which a bellows supporting ring I! is clamped. The two-parthousing and the bellows supporting ring are maintained in assembledrelationship by welding or in any other suitable manner. A bellows I8 issealed to the bellows supporting ring i1, and the bellows defines withthe upper part I! of the housing a closed chamber which is charged withany suitable noncondensable gas, such as nitrogen. A slide valveassembly is located in the lower part it of the housing. This valveassembly includes a valve guide is I which is secured to the part It andextends through an opening in this part. In order to control the flow ofrefrigerant the valve guide I9 is provided with a plurality oflaterallyextending passages 20, and a valve element 2i, which isdisposed within the guide IS in sliding relationship therewith, isprovided with a plurality of laterally-extending passages 22 arrangedfor cooperation with the corresponding passages or the guide. In orderto provide a passage for flow of refrigerant through the valve alongiarms 26 and 21 by rivets or any other suitable fastening devices.The length of the leaf spring 28 between its clamping points on the arms28 and 21 is greater than the straight line distance therebetween, sothat the spring is forced into a bowed condition. In order that thevalve will operate between its open and closed positions with a snapaction, the valve element 2| is mounted on the central portion of thebowed spring 28. In order to limit the movement of the central portionof the spring 28 in on'edirection of motion so as to secure a snapaction, a stop pin 28 is mounted on a support 88 which is secured-to theguide l8. To limit the movement of the central portion of the spring 28in the opposite direction the valve guide I8 is provided with a shoulder8| which acts as a stop for the valve element 2| at one extreme limit ofthe motion of the valve.

In operation the structure described causes a snap action of the valveto the open and closed positions and prevents the valve from occupyin athrottling position. In the position shown in the drawing the pressureof the vaporized refrigerant from the higher temperature evaporator 4 issuch that the bellows has expanded against the pressure of thenoncondensable gas. When the 4 temperature and hence the pressure of thehigher temperature evaporator 4 is reduced, the bellows is compressedand the valve operating arm 24 moves downwardly. Since the valve andhence the central portion of the bowed spring 28 are prevented fromfurther motion by the shoulder 8| on the guide I8, the ends of thebracket ultimately move beyond the center of the spring 28, carryingwith them the ends of the spring 28. This condition, which occurswhen'the predetermined low temperature has been reached in theevaporator 4, results in a snap action of the spring 28 to its oppositebowed position. This moves the valve element 2| upwardly against thestop pin 28 and moves the passages 22 of the valve element out ofregistry with the corresponding passages 28 of the hollow cylinder todiscontinue flow of vaporized refrigerant from the evaporator 4.Conversely, as the temperature and hence the pressure of the evaporator4 increases above the predetermined minimum the bellows is caused toexpand, carrying with it the valve operating arm 24 and the bracket 25.Further motion of the central portion of the leaf spring 28 is preventedby the stop pin 29, and, when the predetermined maximum temperature isreached, the leaf spring 28 snaps over center to open the valve andallow flow of vaporized refrigerant from the evaporator 4. Since thepressure existing in the evaporator bears a definite relation to thetemperature, this arrangement will maintain a predetermined range oftemperatures in the ev porator 4.

The speciflc valve structure described above is not part of the presentinvention but is described and claimed in my copending applicationSerial No. 759,556, filed July 8, 1947, and assigned to the sameassignee as the present invention.

In the conduit 8 a check valve 82 is provided, and this check valve isarranged to allow flow of vaporized refrigerant from the lowtemperatureevaporator 8 upon the occurrence of a predetermined lowpressure in the suction line I and the intake of the compressor I.

The check valve 82, shown in detail in F18. 2, includes a housing 88 andan internal valve body The valve body 84 is provided with a port 88 anda valve seat 88. A resilient strip 81 which is arranged to lift to openthe valve upon the occurrence oi predetermined low pressure in thesuction line 1 is mounted in the valve body 84 in engagement with thevalve seat 88. A suitable stop 88 is provided to limit the upwardmovement of the strip 81.

In order to provide a lower limit of temperature for the evaporator 8 athermostatic bulb 88 is placed in heat exchange relation with a portionof this evaporator. This bulb is adapted to stop the operation of thecompressor upon the occurrence of a predetermined low temperature in theevaporator 8 and to start the compressor when the temperature in theevaporator 8 rises above a predetermined maximum. The starting andstopping of the compressor is controlled by a bellows 48, which expandsor contracts in ac-' cordance with the temperature of the thermostaticbulb 38. The bellows 48 is arranged to operate a switch 4| for governingthe supply of .power to the motor 8, which drives the compressor i'.

The normal operation of the refrigerating systern is as follows. Theliquid refrigerant is supplied to the higher temperature evaporator 4 isvaporized in evaporator 4 due to the absorption of heat, the vaporizedrefrigerant is withdrawn by the compressor through the conduit 8 andthe,

suction line 1. During this period the pressure in the suction line issufliciently high that,

under the pressure conditons normally prevailing in evaporator 3, thestrip 31 is retained against its seat by its natural resilience, andflow of vaporized refrigerant through the branch suction conduit 8 isprevented. Hence there is substantially no refrigeration in theevaporator 3 and the full capacity of the compressor is utilized toproduce refrigeration in the higher temperature evaporator 4. When thetemperature, and the corresponding pressure, of the higher temperatureevaporator 4 have been reduced to the predetermined minimum, the bellowsi8 contracts to close the valve l4 and stop the flow of vaporizedrefrigerant through the conduit 9. As the compressor continues tooperate the closing of the valve [4 and the resulting stoppage'of theflow of vaporized refrigerant to the intake of the compressor willresult in a lowering of the pressure at the intake of the compressor andin the suction line 1. This lowering of the pressure in the suction line1 also results in a reduction of the pressure acting on the suction lineside of the strip 31. The

strip 31 is then forced from its seat by the pressure higher temperatureevaporator l is blocked by the valve I4, and the full capacity of thecompressor is utilized to produce refrigeration in the low temperatureevaporator 3. The restricting tube I2 is arranged, as previouslydescribed, at the normal liquid level of the refrigerant in theheaderll, so that, during the operation of the low temperature evaporator, theliquid refrigerant flowing through the restricting tube 6 builds up theliquid level in the header H and is conducted through the tube i2 to thelow temperature evaporator I. The compressor continues to operate,withdrawing vaporized refrigerant from the low temperature evaporatorwith the resultant reduc tion in the temperature thereof until apredetermined low temperature is reached in this evaporator. Thethermostatic bulb 39 then causes the switch 4| to open, breaking thecircuit to the motor 5 and stopping the operation of the compressor I.

While I have shown a particular embodiment of my invention incorporatedin a two-temperature refrigerating system, I do not desire my inventionto be limited to the specific construction shown and described and Iintend in the, appended claims to cover all modifications within thespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a refrigerating system, a plurality of evaporators adapted tooperate at different temperatures, means for supplying refrigerant tosaid evaporators, means for withdrawing refrigerant from saidevaporators, means responsive to the pressure in one of said evaporatorsfor controlling the flow of vaporized refrigerant'from said one of saidevaporators to said withdrawing means,

' and means for, controlling the flow of vaporized responsive devicebeing dependent on the pressure in one of said evaporators forcontrolling communication between said one evaporator and said suctionline through said one branch line, and means in the other of said branchlines for controlling communication between the other of saidevaporators and said suction line, said last-named means being efiectiveto provide communication between said other evaporator and said suctionline upon the blocking of said one branch line by saidpressure-responsive device.

3. In a refrigerating system, a plurality of evaporators adapted tooperate at different temperatures, means for supplying liquidrefrigerant to said evaporators, means for withdrawing vaporizedrefrigerant from said evaporators, a pressure-responsive device forcontrolling flow of vaporized refrigerant from one of said evaporatorsto said withdrawing means, a pressure-responsive device for controllingflow of vaporized refrigerant from the other of said evaporators to saidwithdrawing means, said second pressure-responsive device being adaptedto open for flow of vaporized refrigerant on the blocking of the flow ofvaporized refrigerant from said one of said ,,evaporators by said firstpressure-responsive desponse to the-blocking of flow of vaporizedredevice inone ofsaid branch lines, said pressure I REFERENCES crrEn"The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Da Number Y te Briggernan et al. Jan. 25. use

